<?php


/**
 * 基于xxtea加密算法实现.
 *
 * @author Qiong Wu <papa0924@gmail.com> 2011-12-2
 * @copyright ©2003-2103 phpwind.com
 * @license http://www.windframework.com
 *
 * @version $Id$
 */
class WindXxtea implements IWindSecurity
{
    /* (non-PHPdoc)
     * @see IWindSecurity::encrypt()
     */
    public function encrypt($str, $key)
    {
        if ($str == '') {
            return '';
        }
        if (!$key || !is_string($key)) {
            throw new WindException('[security.WindXxtea.encrypt] security key is required.',
                WindException::ERROR_PARAMETER_TYPE_ERROR);
        }
        $v = $this->str2long($str, true);
        $k = $this->str2long($key, false);
        if (count($k) < 4) {
            for ($i = count($k); $i < 4; $i++) {
                $k[$i] = 0;
            }
        }
        $n = count($v) - 1;

        $z = $v[$n];
        $y = $v[0];
        $delta = 0x9E3779B9;
        $q = floor(6 + 52 / ($n + 1));
        $sum = 0;
        while (0 < $q--) {
            $sum = $this->int32($sum + $delta);
            $e = $sum >> 2 & 3;
            for ($p = 0; $p < $n; $p++) {
                $y = $v[$p + 1];
                $mx = $this->int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ $this->int32(
                    ($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
                $z = $v[$p] = $this->int32($v[$p] + $mx);
            }
            $y = $v[0];
            $mx = $this->int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ $this->int32(
                ($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
            $z = $v[$n] = $this->int32($v[$n] + $mx);
        }

        return $this->long2str($v, false);
    }

    /* (non-PHPdoc)
     * @see IWindSecurity::decrypt()
     */
    public function decrypt($str, $key)
    {
        if ($str == '') {
            return '';
        }
        if (!$key || !is_string($key)) {
            throw new WindException('[security.WindXxtea.decrypt] security key is required.',
                WindException::ERROR_PARAMETER_TYPE_ERROR);
        }
        $v = $this->str2long($str, false);
        $k = $this->str2long($key, false);
        if (count($k) < 4) {
            for ($i = count($k); $i < 4; $i++) {
                $k[$i] = 0;
            }
        }
        $n = count($v) - 1;

        $z = $v[$n];
        $y = $v[0];
        $delta = 0x9E3779B9;
        $q = floor(6 + 52 / ($n + 1));
        $sum = $this->int32($q * $delta);
        while ($sum != 0) {
            $e = $sum >> 2 & 3;
            for ($p = $n; $p > 0; $p--) {
                $z = $v[$p - 1];
                $mx = $this->int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ $this->int32(
                    ($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
                $y = $v[$p] = $this->int32($v[$p] - $mx);
            }
            $z = $v[$n];
            $mx = $this->int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ $this->int32(
                ($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
            $y = $v[0] = $this->int32($v[0] - $mx);
            $sum = $this->int32($sum - $delta);
        }

        return $this->long2str($v, true);
    }

    /**
     * 长整型转换为字符串.
     *
     * @param long $v
     * @param bool $w
     *
     * @return string
     */
    private function long2str($v, $w)
    {
        $len = count($v);
        $s = array();
        for ($i = 0; $i < $len; $i++) {
            $s[$i] = pack('V', $v[$i]);
        }

        return $w ? substr(implode('', $s), 0, $v[$len - 1]) : implode('', $s);
    }

    /**
     * 字符串转化为长整型.
     *
     * @param string $s
     * @param bool   $w
     *
     * @return Ambigous <multitype:, number>
     */
    private function str2long($s, $w)
    {
        $v = unpack('V*', $s.str_repeat("\0", (4 - strlen($s) % 4) & 3));
        $v = array_values($v);
        if ($w) {
            $v[count($v)] = strlen($s);
        }

        return $v;
    }

    /**
     * @param int $n
     *
     * @return number
     */
    private function int32($n)
    {
        while ($n >= 2147483648) {
            $n -= 4294967296;
        }
        while ($n <= -2147483649) {
            $n += 4294967296;
        }

        return (int) $n;
    }
}
